expand_number(3) support for tmpfs -o size and -o maxfilesize

[Alexander Best]

On Mon Dec 13 10, Oliver Fromme wrote:
> Alexander Best wrote:
>  > is it possible to get support for something like this fstab entry?
>  > 
>  > tmpfs                   /tmp            tmpfs   rw,mode=1777,size=500m  0       0
> 
> expand_number(3) is a libc function which is availbale to
> userland, but the size= argument is parsed by the kernel.
> We don't have something like expand_number() in the kernel.
> A few parts of the kernel have grown their own:
> 
> getenv_quad() in kern/kern_environment.c
> gv_sizespec() in geom/vinum/geom_vinum_share.c
> 
>  > tmpfs doesn't seem to handle humanzied numbers that well. df -h reports:
>  > 
>  > Filesystem         Size    Used   Avail Capacity  Mounted on
>  > tmpfs               17G     12M     17G     0%    /tmp
> 
> That's expected behaviour ...  The function vfs_scanopt()
> is used to parse the size argument using the "%qu" format,
> expecting the number in bytes.  So if you write "500m",
> it stops at the "m" and simply parses the number as 500
> bytes, which is below the minimum size (4 KB), so it falls
> back to the default maximum size which is the total amount
> of memory available (RAM + swap).

i see. since the "m" gets ignored there's no chance of detecting a value
that doesn't comply to the "%qu" format? and maybe issuing a warning that the
size value was invalid?

adding extra code which resembles expand_number() seems overkill in this case
imo.

cheers.
alex

> 
> Best regards
>    Oliver
> 
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